synapse and neuromuscular junction

Can anyone give me some differences and similarities between the two.

Also can anyone explain the terms motor unit, and gradation of response in a clearer way than my crap textbook.

Reply 1

Pallas Athena

2

Motor unit im not so sure but response goes something like this:
An impulse arrives at the neuron and this causes action potentials to travel down it.
This causes calcium ion channels on the pre-synaptic membrane (neuron membrane) to open so calcium ions move from the synaptic cleft to the neuron membrane.
This cause the neurotransmitter vesicles in the synaptic knob to fuse with the neuron membrane.
These neurotransmitters then attach to the receptors on the sacrolemma of a muscle fibre.
This cause a conformational change in the shape of the receptors such that sodium ion channels on the sacrolemma open.
The influx of these sodium ion channels depolarize the sacromere and if it is above the threshold (about -50mv if im not wrong) an action potential is triggered.

HOPE THAT HELPS! :smile:

Reply 2

Mike-nificent

OP

Original post by sneha.vag

Motor unit im not so sure but response goes something like this:
An impulse arrives at the neuron and this causes action potentials to travel down it.
This causes calcium ion channels on the pre-synaptic membrane (neuron membrane) to open so calcium ions move from the synaptic cleft to the neuron membrane.
This cause the neurotransmitter vesicles in the synaptic knob to fuse with the neuron membrane.
These neurotransmitters then attach to the receptors on the sacrolemma of a muscle fibre.
This cause a conformational change in the shape of the receptors such that sodium ion channels on the sacrolemma open.
The influx of these sodium ion channels depolarize the sacromere and if it is above the threshold (about -50mv if im not wrong) an action potential is triggered.

HOPE THAT HELPS! :smile:

Thanks but that I wanted to know the definition of "gradation of response" meant, I know how a response is triggered.
Thanks anyway. + rep for trying :smile:

Reply 3

ash92:)

22

Original post by Mike-nificent

Thanks but that I wanted to know the definition of "gradation of response" meant, I know how a response is triggered.
Thanks anyway. + rep for trying :smile:

Er..I think by that your text book means how long the neurotransmitter is bound for to the post synaptic neuron. The neurotransmitter must bind to receptors on the next neuron to pass the signal on. As long as it is bound, it will keep stimulating the neuron, so enzymes in the synapse eg acetylcholinesterase degrade the neurotransmitter to release it from the receptor. The degraded neurotransmitter is the taken up by reuptake mechanisms and recycled.

:smile:

Reply 4

Ihategcse

10

Neuromuscular junction is a type of synapse.

A motor unit is the a group of muscle cells that are supplied by the same motor neurone.

I am not too sure what you mean by gradation of response, as you may know action potentials are 'all or nothing' so same amplitude regardless of strength of stimulus.

The only thing i can infer if it is related to 'motor units' is:

When you're undertaking more vigorous exercise/activity then you get more motor units e.g. more muscle fibers/cells recruited, hence larger response. The more motor units activated, the more forceful the contraction is going to be.

What does your textbook say, maybe I can help you better if I know what response it is talking about

synapse and neuromuscular junction

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